Interview Questions On React JS.pptx

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Q1). Advantages of React JS in 2022 with its
Limitation
 React JS is open source platform as well as SEO friendly. It is used by both Innovative
Startups and Fortune 500 Companies. Sites using React JS are Netflix, Dropbox,
Dailymotion, American Express, GoDaddy, Coursera, BBC, MDB, Mochi-Pet
Supplies and Food, NewYork Times etc.
 To know more about advantages we can define React JS in few words i.e. Advanced,
Non-Risky, Responsive or as Follows-
1. Abstract and Encapsulation of code.
2. Increase speed by importing feature with synchronized UI System.
3. Don’t need to write whole scripting code. Just need to write the state and declare its

Q2). Role of Virtual-DOM and how it effects
with React JS
Document object model contain record of scripts and when it comes
with react JS it can be called as Virtual DOM or React DOM. React
DOM is actually the virtual copy of Actual DOM which is created when
you modify or update using React and React then make changes to
Actual DOM by creating its Virtual DOM. It’s quite expensive because
browser take time to calculate CSS, all margins, Layouts, JSS modifying
queries etc. As it’s expensive to make changes in Actual DOM so React
created its Virtual DOM as copy and make changes in it and then later
changes in Actual DOM will made.

Q3). What do you meant by Import and
Export in React and writes its Syntax.
It’s very Important and main feature in React which makes it more
useful and make process faster. Importing Files meant to be calling
data from other files easily by giving export access to files. When we
use different components in code, Import and Export helps to
communicate with different code files of components.

Q4). How Classes or Class components are
created in React, Explanation and its Syntax?
React JS create class components with and without ES6. When you
create classes without ES6 then following syntax is used-:
Var create React Class = require (‘create-react-class’);
Var Greeting = create React Class({
Render: function () {
Return < h1>Hello,
{this.props.name}</ h1>;
}
});
Moreover, with create React Class(), you have to provide separate
get Initial State method that returns initial state:

Q5). Different Types of Components in react
IN REACT JS CONTAIN TWO TYPES OF COMPONENTS
1.Stateless Functional Components
These are JavaScript Function as-:
Function welcome(props) {
Return < h1>Hello, {props.name}</ h1>; }
2.Stateful Class Component
These are components having ES6 or regular classes that extend
component class from react library. It must contain Render method
returning HTML
Class welcome extends React.Component (
render() {
return < h1> Hello, {this.props.name} </ h1>;
}
)

Q6). State v/s Props in React?
React make it easy to manage the data and rendering of data when
data changes. Two main ways to think about data in react is states and
props.
Props are useful in passing the arguments to the components we are
creating. It handles components outside updating for example-
increment and decrement of counter Component. As when we create a
class and its constructor so to pass constructor to a class props declare
differently. It’s mostly used for static activities.
State
State is about to handle inside process of the component. State is
mainly used to handle update storing activity and rendering of
component of what user has been done. It is used for dynamic
activities.

Q7). Which Middleware or Function used to
handle asynchronous dispatching of actions?
Redux Reducer is used to handle asynchronous dispatching. Mainly
three things are there to be noted in code i.e. state, actions and reducer.
Const redux = require(‘redux’)
Const create Store = redux.createstore
Const initial State = {
Loading: false,
Users: [],
Error: ‘’
}
CONST FETCH_USERS_REQUEST =
‘FETCH_USERS_REQUEST’
Const FETCH_USERS_SUCCESS =
‘FETCH_USERS_SUCCESS’

Q8). Explain Pure Component?
Pure components compare old states and objects to new states and
objects to decide that re-rendering should happen or not for updating.
If old states and objects are same with new code then pure component
in react don’t allow re-rendering of functions. So, if we extend class
component with pure component then there is no need to apply should
Component Update () lifecycle method. It is helpful in making
application faster while in case of regular components, it will always
re-render either value of states and props changes or not.

Q9). Explain Commands as follows-:
Following are the commands:-
Set State()-:
It is a command in react which set the schedule for updation like clock
components etc. and triggers when updation needed and set to
rendering of code of the page.
Render()-:
When we create application Code written in components that will
translated into elements that get mounted into DOM. React application
splits into two phases that is render phase and commit phase. When
traversing is done, while creating the elements Create element () is
used and then works on DOM will start after creating and go to
Commit phase.

Q10). Explain use of React Component API-
find DOM Node method?
For DOM manipulation ‘find DOM Node’ method is used. Before we
apply this we have to declare object in body as -:
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< button onClick=(this.findDOMNodeHandler)> Find
DOM Node </ button>
< div id=”myDiv”>Dom Node </ div>
findDOMNodeHandler= () => {
let myDiv = document.getElementById(“myDiv”)
ReactDOM.findDOMNode(myDiv).style.color=”green”
}

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